[faraday] Add hostname to faraday annotation

[tinchi]

Faraday integration is not very informative right now:

So i added hostname to the resource name

[delner]

Thanks for the contribution @tinchi! I think this could be a good change, since you're right... GET isn't very useful in itself. The technical implementation details seem fine. I also think it might be worth considering how this interplays with the UI and the intent there.

The resource field typically represents a group of traces, each of which you might consider an instance of the same "thing". So what's the right granularity here for a Faraday trace? GET seems too broad. Adding the host seems to be better. Should it also include the path or query string too?

Without trying to expand the scope on this PR too much, I'm going to think on this a bit, so we know how this fits into making Faraday better.

[tinchi]

@delner by using only hostname i would get a better overview of how particular host behaves in terms of latency and error rate. because right now i only see only latency and error rate by request type:

ideally i would want it to look like this:

but don't think its possible to implement

[delner]

@tinchi Is that bottom screenshot something you photoshopped? (For sake of example?)

[tinchi]

@delner yeah just few tweaks in the chrome's dev console

[delner]

@tinchi Could we rebase this on 0.13-dev? Looks like there's a merge conflict since we migrated the Faraday minitests to RSpec.

[tinchi]

@delner gonna do it shortly

[delner]

This seems related to #277 since they are both concerned with assigning better resource names to traces of HTTP requests. We'll likely want to make the behavior consistent across each of these HTTP clients, so we should probably address what that looks like there before we move ahead with this change. This behavior is still currently up for discussion.